Industrial air-jet looms are complicated pieces of equipment. Such looms weave thousands of threads to create a desired fabric. As a result, an industrial loom has many intricate parts that must operate in conjunction one with another to create the resulting fabric.
In order to accomplish this result, industrial looms perform certain operations. For example, such looms engage in a shedding operation whereby the longitudinal or warp threads are divided or opened, a picking operation whereby the weft thread is inserted between the divided warp, and a beating operating whereby the reed strikes the weft thread into position in the fabric. The warp threads travel through the loom under a certain tension. During the performance of any of the above-described operations, it is known that a warp thread may break or slacken. In such an event, the thread is either omitted or mis-woven to such an extent that the resulting fabric is unacceptable. The prior art has recognized this problem and provided devices that detect warp yarn breaks or slacking. Once detected, the loom is stopped to facilitate repair of the thread.
Described more particularly, it is known to provide an industrial loom with electrically conducting metal elements that extend in a direction parallel with the weft thread. The metal elements extend the entire width of the fabric and are positioned over the warp. A plurality of drop wires, one for each of the thousands of threads, are positioned over and about the metal elements. As there may be thousands of threads, these are also thousands of corresponding drop wires closely aligned along the length of the metal elements. The drop wires are supported in position by warp threads. If a warp thread breaks, the drop wire supported by that thread falls gravitationally onto one of the electrically charged metal elements. The drop wire bridges or short-circuits that metal element and completes an electrical connection for stopping the loom. Once the loom has stopped, the operator checks the loom to determine which thread had broken, effects repair of that thread and restarts the loom.
It can be difficult for the operator to determine which drop wire has fallen. In some cases, the operator may not be able to see the fallen drop wire and need to run his or her hand over all of the drop wires in a "hunt-and-peck" like fashion to locate the one that has fallen. Various devices have been proposed to assist the operator in this effort. For example, U.S. Pat. No. 3,725,911 discloses a stop motion device with a selective indicator for a multi-threaded textile machine. The device includes a number of thread slack-detection switches, each having an indicator lamp. A four-layer diode is provided to complete a circuit and thereby stop the motion of the loom machine and to light the relevant indicator lamp. In this fashion, the machine operator is appraised of which thread affected stoppage of the machine.
Another such device is shown in U.S. Pat. No. 4,321,951 to Hintsch, which discloses a warp yarn stop motion device. This patent describes a sub-divided locating rail connected with pilot lights at the end of each section. Should a drop wire fall onto a rail section, the pilot lights at the end of that section are illuminated to identify the section of the rail within which a broken warp thread is located.
As indicated above, the drop wires are supported by the warp threads. These threads travel through the loom, under tension, at significant speed. The drop wires are preferably of a lightweight material that will not gravitationally displace the thread due to its own weight. As each thread is provided with a drop wire, the drop wires must also be relatively thin in dimension. As a result of these structural considerations and due to the action of the thread passing therethrough, the drop wires become worn and pliable. The drop wires seemingly "dance" about the metal elements and, once sufficiently worn and pliable, will twist or otherwise contact a metal element even though the supporting thread is neither broken nor slack. Nevertheless, the loom will stop automatically because contact of the drop wire and the electrically-charged metal element will bridge or short-circuit the element and complete the electrical connection for stopping the loom. This condition is referred to as a "false warp stop."
In the event of a false warp stop, the operator must search for the offending drop wire. However, once the loom stops, the offending drop wire typically returns to its initial position and will appear to be in good working order. The operator will restart the machine, but the offending drop wire will inevitably twist again and stop the loom. Upon restarting the machine, any indicator lamp that may have been illuminated will be turned off automatically. The indicator lamp will not be activated again until the drop wire touches the metal element, either due to a broken or slackened thread, or due to a false warp stop. It is to be understood that, in many commercial weaving facilities, one operator will be responsible for many looms. To find an offending drop wire that has caused a false warp stop, the operator will restart the loom, causing any indicator lamp to be switched off. Thus, while the operator's attention may be necessarily directed to other looms, any initial indication of the location of the offending wire is readily forgotten. The operator typically requires such additional indication in order to search for a fallen drop wire, let alone an offending drop wire causing false warp stops. Thus, the operator may have to watch and wait for that one machine until the offending wire causes another false warp stop. Such a process is indefinite, time consuming, impractical, and many times impossible.
When an industrial loom machine experiences repeated false warp stops, the efficiency of the weaving process suffers significantly. It is not uncommon for several operators to work together in order to identify the failing or offending drop wire. In such cases, cost of effecting the repair is increased further due to the manpower needed to identify the offending drop wire and the downtime experienced while the operator or operators search for the offending drop wire.
Thus, there is a need in the prior art for a device that assists in the identification and detection of an offending drop wire so as to save loom downtime and repair costs.